Toxicity

Toxicity is the degree to which a substance can damage an organism, depending on the dose, the route and duration of exposure, and the species and individual exposed.

Toxicologists distinguish acute toxicity from a single large exposure, chronic toxicity from repeated smaller exposures, and organ-specific toxicity such as hepatotoxicity affecting the liver. A basic principle is that the dose makes the poison: almost any substance is harmful at some level and harmless at another, so safety is described in terms of thresholds, margins and no-observed-adverse-effect levels found in animal studies before human trials begin.

Species differences matter. Dogs are far more sensitive to THC than people because they have a higher density of cannabinoid receptors in the brain, so accidental ingestion of THC products by dogs is a recognized cause of veterinary emergency visits, and any signs of poisoning in a pet call for immediate veterinary care. For CBD in people, the main toxicity signals in clinical trials have been liver enzyme elevations at high prescription doses, especially alongside certain seizure medications. In products, toxicity concerns also cover contaminants such as heavy metals and residual solvents.